In the never-ending struggle to produce cheaper, faster, and more reliable computer systems, power consumption has taken on a significant role. Specifically, power to operate the disc drive is supplied by the computer; therefore, the voltage and current demands of the disc drive must meet the specifications that are imposed by the computer power supply capabilities. As development of computer systems have progressed, the amount of power available to disc drives has decreased or remained the same while the speed (revolutions-per-minute) and capacity of the disc drive has increased. As disc drives achieve faster revolutions-per-minute (RPMs), the amount of power needed to achieve the faster RPMs could also increase. Thus, there is a need to control and limit the amount of power used by the disc drive.
One way to accomplish controlling and limiting the power consumed by the disc drive is to monitor and limit the peak motor current through the spindle motor of the disc drive. An example of this is described in U.S. Pat. No. 5,216,343 (Genheimer et al.).
While this method is effective in controlling the peak current through the spindle motor, it does not uniformly control the current drawn from the power supply. In fact, significant peaks in the current drawn from the power supply exist at multiple stages during the motor spin-up. These peaks can cause instability, dropouts, and power faults in some power supply systems.
Due to the highly competitive nature of the disc drive industry, it is necessary to produce disc drives which meet customer requirements at the lowest possible price. One method to accomplish this is to lower costs by reducing the number of components needed within the disc drive. This highlights another problem associated with controlling the peak current through the spindle motor: the control mechanisms require additional electronics and hardware components to be added to the disc drive.
The present invention provides a solution to these and other problems, and offers other advantages over the prior art.